ChessBase for Coaches: The Thornton Trap

by Jeffrey Ashton
4/26/2022 – In the Thornton Trap, a player castles queenside, giving check, to win an unprotected rook. National Master Jeffrey Ashton discusses the Thornton Trap and how to search for examples of it using the ChessBase Manoeuvres Search.

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The Thornton Trap

In the Thornton Trap, or “the Thornton castling trap,” a player castles queenside, giving check, to win an unprotected rook. The diagram below shows a typical example.

If 1…Rxb2? White wins the black rook with 2.0-0-0+!

According to chess historian Edward Winter, the earliest example of this trap was in Thornton-Boultbee, 1884.  

Lessons from the Thornton Trap

Aside from being a nice tactic with a fun name, coaches should teach the Thornton Trap to students of all levels, for a few reasons. The Thornton Trap:

  • teaches beginners about castling queenside, and introduces the idea that castling is not only a defensive move. 
  • is a simultaneous attack. Two chessmen (a king and a rook) are threatening two targets, a loose rook and a king. This is different from a fork or other double attacks.
  • demonstrates a blind spot in chess. Students can discuss why a good tactician might fall into this trap. Perhaps it has something to do with the unique movements of castling queenside. Maybe it has something to do with humans overlooking “sideways moves.” Possibly, a player forgets that the loose rook on b2 can be threatened. Or maybe players don’t think about castling so late in a game. Discussing blind spots and asking, “why do people blunder?” might help reduce blundering and improve tactical awareness.  

Manoeuvres Search to find Thornton Traps  

ChessBase Manoeuvres Search can be used to find many chess patterns. To do a ChessBase Manoeuvres Search to find Thornton Traps:

1. In the Database window, right click on your Reference Database (or your largest database). Click on Search.

2. In the basic Search Database window, click Advanced.

3. In the Advanced Search Database window, first click Reset. Useful Tip: If you ever have any problems doing a ChessBase search, try clicking Reset and try again.

4. Click on the Position tab. Set up the board as shown below. For this example, it’s intentional that there is no Black king. In the next step, we will search for checks, so ChessBase will know where to “place” the Black king when searching. Alternatively, you can simply place a Black king on d8 or d7, but you will get fewer search results

5. Click on the Manoeuvres tab. Click Insert/New. In the piece box, select K for King. In the next box, type in e1. In the box after that, type c1. Click on the “Check” box. We are telling ChessBase to search for games where White moves the King from e1 to c1 (castling queenside), checking Black’s king. Click OK and ChessBase will start searching.

6. The search results should look something like this but might differ depending on the database you are using.

7. Click on any game in the Search Result list. Press Control + A to select all games. Right click on the highlighted games -> Output -> Database. Name the file "Thornton Traps" or you can select a file that already exists, and ChessBase will add the games to the file.

Finally, you can load your Thornton Traps file, and delete any games that you don’t want to show your students. Annotate, print, or share the ones that you like best. You can even create a worksheet where the solution to every puzzle is 0-0-0+!.


Jeffrey Ashton is a US Chess National Master. He teaches chess, organizes tournaments, and owns the Panda Chess Academy in Houston, Texas. He attended The University of Texas at Dallas on a full-ride chess scholarship, graduating with a degree in psychology.